Stock material or miscellaneous articles – All metal or with adjacent metals – Foil or filament smaller than 6 mils
Reexamination Certificate
2000-04-11
2001-09-18
Gorgos, Kathryn (Department: 1741)
Stock material or miscellaneous articles
All metal or with adjacent metals
Foil or filament smaller than 6 mils
C205S077000, C205S097000, C205S291000, C204S206000, C204S211000, C204S212000
Reexamination Certificate
active
06291080
ABSTRACT:
FIELD OF INVENTION
This invention relates to electrodeposited copper foil, particularly ultra-thin copper foil, and to a process and apparatus for producing such foil, wherein the outer edges of a web of copper foil as produced on a rotating drum cathode machine are thicker than the central portion of the web, so as to reduce the tendency for the foil to tear when it is stripped from the drum cathode.
BACKGROUND OF THE INVENTION
Copper foil for use in the manufacture of copper-clad laminates used in making printed circuit boards (PCB's) is usually made on a rotating drum cathode machine. In this method copper is electrodeposited on a rotating cylindrical drum cathode by passing an electric current from a lead, or lead-antimony, anode (usually two anodes) through a copper-containing electrolyte such as, an aqueous copper sulfate/sulfuric acid solution, to plate copper on the surface of a rotating drum cathode partially immersed in the electrolyte. The drum cathode typically has an outer top sheet formed of titanium or a similar metal. As the drum rotates, copper is plated onto the outer surface of the top sheet, and a web of raw copper foil is continuously stripped from the drum surface and coiled. Such stripping is possible because the top sheet of the drum is made of a metal such as titanium, which provides a low adhesion between the plated copper foil and the surface of the top sheet.
The thickness of the copper foil plated on the drum cathode is determined by a number of variable process parameters, and it is known to produce thin copper foil and ultra-thin copper foils, i.e., one-half ounce or less foils (those having a normal thickness of about 17 microns nominal thickness or less). However, the production efficiency of electrodeposited copper foil, especially ultra-thin copper foil, is reduced by a tendency for the raw foil to tear during the course of the processing. This problem is especially severe when very thin foil is being stripped from the drum cathode. This tearing problem makes the production of copper foil having a nominal thickness of 12 microns, or especially 9 micron foil, extremely difficult and uneconomical due to the extremely low production yields.
SUMMARY OF THE INVENTION
A primary object of the present invention is a copper foil, together with a process and apparatus for producing such foil, which overcomes the above-mentioned problems in prior art processes for producing copper foil.
Another object is a process, and apparatus, for producing ultra-thin copper foil, wherein tearing of the raw foil during processing is significantly reduced.
The above and other objects of the invention will become apparent from the following description of preferred embodiments of the invention and may be achieved by an elongated web of electrodeposited copper foil produced on a rotating cathode drum machine, comprising a central portion of the web extending longitudinally along the length of the web; and two edge portions of the web extending along the length of the web, one on either side of the central portion, wherein the central portion has a nominal thickness, and the edge portions each have a nominal thickness greater than that of the central portion.
The invention also provides an improved process for producing electrolytic copper foil wherein an electric current is passed from an anode through a copper-containing electrolyte to a rotating drum cathode spaced from the anode to electrodeposit copper foil on the cathode, which comprises passing an electric current from a central portion of the anode to an opposed central portion of the cathode, each of the central portions having a width less than the total width of the cathode, at a first current density; and simultaneously passing an electric current from the edge portions of the anode positioned outwardly of and adjacent the central portion of the anode to an opposed edge portion of the cathode at a second current density which is greater than the first current density to electrodeposit on the cathode a copper foil having edge portions thicker than the central portion thereof.
There is also provided a rotating drum cathode machine for producing copper foil comprising
(a) a rotating drum cathode having a width extending in a direction parallel to an axis about which the drum rotates;
(b) at least one anode facing and spaced from the cathode, and having a width extending in a direction parallel to said cathode axis, the anode including a anode central portion having a width less than the width of the cathode, and two anode edge portions, each being positioned adjacent an outboard edge of one of the anode edge portions;
(c) the anode central portion being capable, during use of the machine, of passing an electric current from the anode central portion to the cathode at a first current density; and
(d) the anode edge portions being capable, during use of the machine, of passing an electric current from each of the anode central portions to the cathode at a second current density which is greater than the first current density.
REFERENCES:
patent: 5326455 (1994-07-01), Kubo et al.
Gaskill George
Yates Charles B.
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Gorgos Kathryn
Parsons Thomas H
Yates Foll USA, Inc.
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